QDoc: Remove `QmlCodeParser::m_lexer`

As part of producing a documentation set, QDoc parses a series of
user-defined input source files in various languages to extract the
user-provided documentation and certain source-code level elements.

For QML source files, the `QmlCodeParser` class is used, taking care of
reading the QML code and build an internal representation for some of
its elements.

`QmlCodeParser` uses the `QQmlJs` parsing api to do so.
As part of using the `QQmlJs` parsing api, `QmlCodeParser` has to build
a `QQmlJs::Engine`, `QQmlJs::Lexer` and `QQmlJsEngine::Parser`.

Currently, `QmlCodeParser` stores all those elements as instance
members. For example, for the `QQmlJs::Lexer` instance, a member
variable `m_lexer` is used as storage.
Supposedly, this is intended as a way to avoid building the three
elements more than once.

Building a `QQmlJs::Lexer` more than once does not provide any
meaningful overhead, moreover not in the code path where it is used.
Furthermore, `m_lexer` is used only once, in
`QmlCodeParser::parseSourceFile`, the entry point for parsing a QML
source file.

Hence, to reduce the scope of `m_lexer` and avoid requiring an
out-of-scope initialization for it, `m_lexer` is now removed in favor of
an local instance in `QmlCodeParser::parseSourceFile`.

The initialization and deletion of `m_lexer` in
`QmlCodeParser::initializeParser` and `QmlCodeParser::terminateParser`
was removed as a consequence of the removal of the member.

Some comments that mentioned the initialization or deletion of the lexer
were modified to represent the modified code.

Change-Id: I32d38e7883273ab83745eb1f34d183fd5ecca19a
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

2 files changed, 5 insertions, 7 deletions

diff --git a/src/qdoc/qmlcodeparser.cpp b/src/qdoc/qmlcodeparser.cpp
index 902000954..3d8cd5483 100644
--- a/src/qdoc/qmlcodeparser.cpp
+++ b/src/qdoc/qmlcodeparser.cpp
@@ -16,25 +16,23 @@ QT_BEGIN_NAMESPACE
 /*!
   Constructs the QML code parser.
  */
-QmlCodeParser::QmlCodeParser() : m_lexer(nullptr), m_parser(nullptr) { }
+QmlCodeParser::QmlCodeParser() : m_parser(nullptr) { }
 
 /*!
   Initializes the code parser base class.
-  Also creates a lexer and parser from QQmlJS.
+  Also creates a parser from QQmlJS.
  */
 void QmlCodeParser::initializeParser()
 {
-    m_lexer = new QQmlJS::Lexer(&m_engine);
     m_parser = new QQmlJS::Parser(&m_engine);
 }
 
 /*!
-  Terminates the QML code parser. Deletes the lexer and parser
+  Terminates the QML code parser. Deletes the parser
   created by the constructor.
  */
 void QmlCodeParser::terminateParser()
 {
-    delete m_lexer;
     delete m_parser;
 }
 
@@ -82,7 +80,8 @@ void QmlCodeParser::parseSourceFile(const Location &location, const QString &fil
 
     QString newCode = document;
     extractPragmas(newCode);
-    m_lexer->setCode(newCode, 1);
+    QQmlJS::Lexer lexer{&m_engine};
+    lexer.setCode(newCode, 1);
 
     if (m_parser->parse()) {
         QQmlJS::AST::UiProgram *ast = m_parser->ast();
diff --git a/src/qdoc/qmlcodeparser.h b/src/qdoc/qmlcodeparser.h
index 91ee64858..bbf2a1545 100644
--- a/src/qdoc/qmlcodeparser.h
+++ b/src/qdoc/qmlcodeparser.h
@@ -34,7 +34,6 @@ public:
 
 private:
     QQmlJS::Engine m_engine {};
-    QQmlJS::Lexer *m_lexer { nullptr };
     QQmlJS::Parser *m_parser { nullptr };
 };